The present invention relates to a plug-in connection system, in particular for fluid lines, fittings, or assemblies, comprising a first coupling part, such as a housing part, and a second coupling part, such as a plug part, which can be plugged into a receiving opening of the first coupling part along an axis, wherein a holding element for latching with a counter holding element of the other coupling part is arranged on one of the two coupling parts, wherein the holding element has a spreading surface which, by sliding relative to a counter spreading surface of the counter holding element, causes a spreading movement of the holding element transversely to the axis by a spreading path under the action of a an installation force when being plugged in by an installation path.
An embodiment of a plug-in connection of this general type is known from WO 2006/018384 A1. This document describes a plug-in connection for fluid lines, consisting of two coupling parts, which can be plugged together, namely in particular a sleeve part and a plug part, wherein the sleeve part can be plugged in a sealing manner into a receiving opening of the plug part with a plug shaft, and which can be detachably locked by means of a locking device when it is plugged in, the locking device consisting, on the one hand, of two external, radial, flange-like, and in plugged state axial, in plug-in direction adjacent holding bars of the two coupling parts, on the other hand, at least one holding part, which axially and radially positively encompasses the holding bars of both coupling parts with at least one axially C-shaped holding section. The holding element is configured on the holding part for latching with the counter-holding element, which also has the spreading surface, while the counter-holding element with the counter-spreading surface is formed by the holding bar of the sleeve part. The spreading surface and the counter-spreading surface each have a conical configuration, so that they substantially fully slide onto one another when plugged in.
WO 2006/018384 A1 describes a technical solution that makes it possible, maintaining the advantages of the known locking principles, to reduce the risk of losing the holding element and to simplify installation, even in application cases in which only a small surrounding space is available at the installation site. The known coupling device has proven itself in practice under the name VOSS plug-in system 246 for many different applications. In particular, in an embodiment of the plug-in system designated VOSS 246 AX, which preferably can be used for connecting fuel lines and assemblies, it allows quick connect. The system is mounted by plugging the plug part, onto which the holding part has already been premounted, into the housing or sleeve part, the holding element of the plug part latching with the counter-holding element of the housing part. It has been shown that undesired high plug-in force maxima occasionally occur with this type of installation during the plug-in process.